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One pathogen two stones: are Australian tree frog antimicrobial peptides synergistic against human pathogens?
Ist Teil von
European biophysics journal, 2017-10, Vol.46 (7), p.639-646
Ort / Verlag
Cham: Springer International Publishing
Erscheinungsjahr
2017
Quelle
MEDLINE
Beschreibungen/Notizen
Antimicrobial peptides (AMPs) may act by targeting the lipid membranes and disrupting the bilayer structure. In this study, three AMPs from the skin of Australian tree frogs, aurein 1.2, maculatin 1.1 and caerin 1.1, were investigated against Gram-negative
Escherichia coli
, Gram-positive
Staphylococcus aureus,
and vesicles that mimic their lipid compositions. Furthermore, equimolar mixtures of the peptides were tested to identify any synergistic interactions in antimicrobial activity. Minimum inhibition concentration and minimum bactericidal concentration assays showed significant activity against
S. aureus
but not against
E. coli
. Aurein was the least active while maculatin was the most active peptide and some synergistic effects were observed against
S. aureus
. Circular dichroism experiments showed that, in the presence of phospholipid vesicles, the peptides transitioned from an unstructured to a predominantly helical conformation (>50%), with greater helicity for POPG/TOCL compared to POPE/POPG vesicles. The helical content, however, was less in the presence of live
E. coli
and
S. aureus
, 25 and 5%, respectively. Equimolar concentrations of the peptides did not appear to form greater supramolecular structures. Dye release assays showed that aurein required greater concentration than caerin and maculatin to disrupt the lipid bilayers, and mixtures of the peptides did not cooperate to enhance their lytic activity. Overall, aurein, maculatin, and caerin showed moderate synergy in antimicrobial activity against
S. aureus
without becoming more structured or enhancement of their membrane-disrupting activity in phospholipid vesicles.